Help, 3ds wont turn on

[Shiraori]

I've found my old 3ds and it had cfw, decided to play some MH4U but its just not booting, the screen stays black and the blue light on the power stays on can't access the luma menu with select or the recovery mode, tried updating luma but then it changes to the blue light turning on and off, asked my friend for his SD card and the 3ds turns on normally with it, i can install games with the FBI and play normally, then I decided to transfers his files to my SD card and i get to the inicial result with 2 black screens and the blue light on. If i try to turn on without sd card it boot normally, i can even go the luma menu and it seems to be on luma 11.0, and it says to be booting from the CTRnand, decided to try and update to the fastboot3ds (with my friend sd card) and it installed normally, i can get to the fastboot menu but only with no sd card when i try with it on it just stay on the black screen and blue light. Can anyone help me? (sorry if bad grammar not english native)
obs: my friend 3ds also dont boot with my sd card is it a problem from the card or im doing something wrong?

 

[Kwyjor]

Your 3DS works fine except when your SD card is inserted, and your friend's 3DS doesn't work when your SD card is inserted into it, so why you are still wondering if there is a problem with your SD card?

Copy everything off your card on a PC (use Roadkil's Unstoppable Copier just in case something is corrupted), format the card, test the empty card with h2testw, and then copy everything back if the test is OK. If the test fails, get a new SD card.